Membrane switch and dial operation member equipped therewith

ABSTRACT

A membrane switch comprises a lower contact sheet having a first conductor, an upper contact sheet having a second conductor, and a spacer interposed therebetween. An application of a press force onto contact areas in the upper contact sheet causes the upper contact sheet to be bent, so that at least one of the contact areas and a corresponding contact area in the lower contact sheet come in contact with each other. The first and second conductors are always connected to each other, since a conductive area in the lower contact sheet is always in contact with a conductive area in the upper contact sheets. Hence, the contact of at least one of the contact areas with the corresponding contact area allows the membrane switch to turn on (ON) by a very small press force and therefore the reliability of the switch operation to be significantly enhanced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a membrane switch, which is produced byinterposing a spacer between flexible films having conductor circuitsformed by the printing or the like. The present invention also relatesto a dial operation member, which is equipped with such a membraneswitch.

2. Description of the Related Art

Such a membrane switch is used as a switch including electricalcircuits, which are formed by printing a conductive paste onto flexiblesubstrates, such as polyester films or the like. The membrane switch isused as a lightweight, thin and flexible switch, and therefore isparticularly useful for mass production. These significant features ofthe membrane switch allow it to be used in a wide application field, forinstance, in a keyboard for a computer, a home electrical appliance, aportable communication device, such as a cellar phone, a component foran automobile, a musical instrument, a medical appliance and others.

FIG. 7 is a plan view of a conventional membrane switch. FIG. 8 is aplan view of a lower contact sheet in the conventional membrane switch.FIG. 9 is a plan view of an upper contact sheet in the conventionalmembrane switch. FIG. 10A is a sectional view of the conventionalmembrane switch in the non-conductive state, and FIG. 10B is a sectionalview of the conventional membrane switch in the conductive state.

Such a conventional membrane switch 110 comprises a lower contact sheet111, an upper contact sheet 112, a spacer 113, a connector 114 andothers, as shown in FIGS. 7-10. The lower contact sheet 111 includes aconductor 111 a and a projection portion 111 b, as shown in FIG. 8. Theconductor 111 a includes several sets of paired contact areas 111 c and111 d, each end of which is ramified in the form of an approximately Ushape. The upper contact sheet 112 includes circular contact areas 112a, which are used to come into contact with the corresponding contactareas 111 c and 111 d in the conductive state, as shown in FIG. 9. Inthe spacer 113, there are through holes 113 a, through which pairedcontact areas 111 c and 111 d on the side of the lower contact sheet 111and corresponding contact areas 112 a on the side of the upper contactsheet 112 come into contact with each other in the conductive state, asshown in FIG. 7. The projection portion 111 b which is part of the lowercontact sheet 111 including part of the conductor 111 a is inserted intothe connector 114.

In the following, the function of the conventional membrane switch willbe described.

When trying to push a projection portion 109 d to bend the upper contactsheet 112 in the lower direction by pushing a projection portion 109 d,as shown in FIG. 10A, the contact area 112 a is in contact with thepaired contact areas 111 c and 111 d, as shown in FIG. 10B. Accordingly,the contact area 112 a is directly connected to the paired contact areas111 c and 111 d, so that the membrane switch 110 turns on in theconductive state (the ON state).

In the conventional membrane switch 110, there is a problem in which adecrease in the press force acting to the upper contact sheet 112occasionally causes the contact area 112 a to come in contact with onlyone of the paired contact areas 111 c and 111 d, so that the membraneswitch 110 does not turn on in the conductive state. Furthermore, inorder to securely connect the contact area 112 a with both the contactareas 111 c and 111 d in the conventional membrane switch 110, it isnecessary that the projection portion 109 d made of a resilientmaterial, such as gum or the like, presses against the upper contactsheet 112 with a press force greater than a predetermined force. Thisalso provides an increase in the production cost, since the number ofthe parts constituting the membrane switch 110 is inevitably increased.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide amembrane switch capable of turning on even with a very small weight.

It is another object of the present invention to provide a dialoperation member, which is equipped with such a membrane switch.

In accordance with a first aspect of the invention, a membrane switchcomprises,

(a) a first base element made of an electrical insulation elasticmaterial, the first base element having a first conductor including atleast one press contact area and at least one permanent contact area ona surface of the first base element;

(b) a second base element made of an electrical insulation material, thesecond base element having a second conductor and a third conductor on asurface facing the surface of the first base element,

the second conductor including at least one press contact area inaccordance with the arrangement of the at least one press contact areain the first conductor, and

the third conductor including at least one permanent contact area inaccordance with the arrangement of the at least one permanent contactarea in the first conductor,

the second base element further having a connector section forconnecting the second and third conductors to an external circuit; and

(c) a spacer made of an electrical insulation material, the spacer beinginterposed between the first base element and the second element, thespacer having through holes at positions corresponding to those both inthe at least one press contact area and the at least one permanentcontact area of the first and second base elements.

In accordance with a second aspect of the invention, a membrane switchcomprises,

(a) a first base element made of an electrical insulation elasticmaterial, the first base element having a first conductor including atleast one press contact area, a second conductor including at least onepermanent contact area and a connector section for connecting the firstand second conductors to an external circuit on a surface of the firstbase element;

(b) a second base element made of an electrical insulation material, thesecond base element having a third conductor on the surface facing thesurface of the first base element, the third conductor including atleast one press contact area in accordance with the arrangement of theat least one press contact area disposed in the first conductor and theat least one permanent contact area in accordance with the arrangementof the at least one permanent contact area disposed in the firstconductor; and

(c) a spacer made of an electrical insulation material interposedbetween the first base element and the second base element, the spacerhaving through holes in accordance with the arrangement of the at leastone press contact area and the at least one permanent contact area.

In accordance with a third aspect of the invention, a dial operationmember comprises,

(a) a shaft;

(b) a bearing through which the shaft passes;

(c) a dial body fixed to the shaft and rotatably supported around thecenter axis of the shaft;

(d) a press member for switch disposed so at to face the dial body forswitching, the press member having at least one press projection portionfor switching; and

(e) one of the above mentioned membrane switches, wherein at least onepress portion for switching is disposed so as to face the at least pressprojection for switching in the press member for switch.

Further objects, features and advantages of the present invention willbecome apparent from the following description of the preferredembodiment with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an operation dial onto which a membraneswitch according to the invention is mounted.

FIG. 2 is a plan view of the membrane switch according to the invention.

FIG. 3 is a plan view of a lower contact sheet in the membrane switchaccording to the invention.

FIG. 4 is a plan view of an upper contact sheet in the membrane switchaccording to the invention.

FIG. 5 is a plan view of a spacer in the membrane switch according tothe invention.

FIG. 6A is a sectional view of the membrane switch according to theinvention in the non-conductive state.

FIG. 6B is a sectional view of the membrane switch according to theinvention in the conductive state.

FIG. 6C is a sectional view of the membrane switch according to theinvention in the conductive state.

FIG. 7 is a plan view of a conventional membrane switch.

FIG. 8 is a plan view of a lower contact sheet in the conventionalmembrane switch.

FIG. 9 is a plan view of an upper contact sheet in the conventionalmembrane switch.

FIG. 10A is a sectional view of the conventional membrane switch in thenon-conductive state.

FIG. 10B is a sectional view of the conventional membrane switch in theconductive state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the accompanying drawings, an embodiment of theinvention will be described in detail.

FIG. 1 is a sectional view of a dial operation member 1, which isequipped with a membrane switch 10 according to the invention.

The dial operation member 1 is used as a device, which has a touchsensing function and is rotatably operated. The dial operation member 1is fixed to a chassis 3 of an electric appliance or the like, whereinthe chassis 3 is covered by a front panel 2. The dial operation member 1is normally used, for instance, in a CD player for DJ, in which case,the dial operation member 1 is operated to temporarily pause the drivingof the CD in the playback state. As shown in FIG. 1, the dial operationmember 1 substantially comprises a dial 4, a shaft 5, a bearing 6, anencoder disk 7, a photo-interrupter 8, a force transmission element 9and the membrane switch 10.

The dial 4 is used as a disk-shaped element, which is capable of beingrotatably manipulated and is made of, for instance, stiff plasticmaterial, aluminum die cast or the like, and the dial 4 has anarch-shaped projection portion 4 a in the circumferential direction.

The shaft 5 is used as an element for rotatably supporting the dial 4,in which case, the dial 4 is fixed to an end of the shaft 5 and theencoder disk 7 is fixed to the other end of the shaft 5.

The bearing 6 is used as an element for rotatably supporting the shaft5, in which case, pins 6 a and 6 b as well as a projection portion 6 care formed on the upper part of the bearing 6 and an adaptation element6 d is disposed in the lower portion of the bearing 6. The bearing 6 isfixed to the bottom surface of the chassis 3 by screws 3 a and 3 b. Theencoder disk 7 is used as a rotary disk, which has a plurality of slitsarranged in the same spacing in the circumferential direction, and iscapable of being rotated together with the dial 4.

The photo-interrupter 8 is used as a device for sensing the speed ofrevolution and the angular position of the encoder disk 7, wherein, oneof the slits in the encoder disk 7 passes through a space between alight-emitting element and a light-receiving element. Thephoto-interrupter 8 is fixed to the adaptation element 6 d.

The force transmission element 9 is used as an element for transmittingthe press force applied onto the dial 4 to the membrane switch 10, andis constituted by a material such as stiff plastic material, aluminumdie cast, or the like in a disk-shape, as similarly to the dial 4. Theforce transmission element 9 includes holes 9 a and 9 b for receivingthe pins 6 a and 6 b, a contact portion 9 c serving to come into contactwith the projection portion 4 a and a projection portion 9 d serving tocome into contact with the membrane switch 10.

In FIG. 1, a gap having a very small spacing is formed between the dial4 and the bearing 6. Similarly, a gap having a very small spacing isformed between the encoder disk 7 and the bearing 6, thereby enablingthe dial 4 and the encoder disk 7 to be moved by a very small amount inthe axial direction of the shaft 5. The gaps are designed such that theencoder disk 7 and the photo-interrupter 8 come into no contact witheach other. When the surface of the dial 4 is pushed downward, the pressforce acts to push down the force transmission element 9 via theprojection portion 4 a. The force transmission element 9 pushes down themembrane switch 10 in response to the movement of the force transmissionelement 9. When stopping the pushing of the dial 4, the forcetransmission element 9 is pushed upwards due to the resilient force ofthe membrane switch 10. In conjunction with this movement, the dial 4 isalso pushed upwards.

FIG. 2 is a plan view of the membrane switch according to the invention.FIG. 3 is a plan view of the lower contact sheet in the membrane switchaccording to the invention. FIG. 4 is a plan view of the upper contactsheet in the membrane switch according to the invention. FIG. 5 is aplan view of the spacer in the membrane switch according to theinvention.

The membrane switch 10 is used as a switch, which is formed byinterposing a spacer 13 between the lower contact sheet 11 including aconductor 11 a and the upper contact sheet 12 including a conductor 12a, and serves to connect one or more of contact areas 11 g in theconductor 11 a to one or more of corresponding contact areas 12 g in theconductor 12 a with the aid of the press force. As shown in FIGS. 2-5,the membrane switch 10 comprises the lower contact sheet 11, the uppercontact sheet 12, the spacer 13 and a connector 14.

The lower contact sheet 11 is a base element including the conductor 11a. The lower contact sheet 11 is formed by printing a conductive pasteprepared by mixing conductive fine particles of copper, carbon, silveror the like with a binder resin is printed onto a polyester film. Asshown in FIG. 3, the conductor 11 a for supplying an electrical current,a projection portion 11 b inserted into the connector 14, a through hole11 c for receiving the projection portion 6 c in FIG. 1, through holes11 d and 11 e for receiving the corresponding pins 6 a and 6 b and athrough hole 11 f for receiving a screw 3 a are formed on the lowercontact sheet 11.

The conductor 11 a is constituted in a wiring pattern by conductorsformed on the surface of the lower contact sheet 11. The conductor 11 acomprises six circular contact areas 11 g coaxially arranged at a radialdistance from the center of the lower contact sheet 11 with the samecircumferential spacing; a conductor portion 11 h formed in thecircumferential direction of the lower contact sheet 11 for connectingto the contact areas 11 g; a connection conductor portion 11 iprojecting from the conductor portion 11 h toward the projection portion11 b; an annular conductive area 11 j for receiving the screw 3 a; andanother connection conductor portion 11 k projecting from the annularconductive area 11 j toward the projection portion 11 b.

The upper contact sheet 12 is used as a base element including conductor12 a. The upper contact sheet 12 is formed by printing a conductivepaste on a polyester film with a similar procedure to that in the lowercontact sheet 11. As shown in FIG. 4, the upper contact sheet 12comprises a conductor 12 a for supplying an electric current; a throughhole 12 c for receiving the projection portion 6 c in FIG. 1; throughholes 12 d and 12 e for receiving the corresponding pins 6 a and 6 b;and a through hole 12 f for receiving the screw 3 a.

The conductor 12 a is constituted in a wiring pattern by a conductorformed on the surface of the upper contact sheet 12. The conductor 12 acomprises six annular contact areas 12 g coaxially arranged with respectto the center of the upper contact sheet 12 with the samecircumferential spacing; a conductor portion 12 h formed in thecircumferential direction of the upper contact sheet 12 for connectingto the contact areas 12 g; and an annular conductive area 12 j connectedto the conductor portion 12 h for receiving the screw 3 a. As show inFIG. 2, the contact areas 12 g are disposed so as to face the contactareas 11 g, and when the contact areas 11 g and 12 g receive a pressforce, the membrane switch turns on in the conductive state. Theconductive area 12 j is disposed to face the contact area 11 g, as shownin FIG. 2, and is connected to the conductor portion 12 h, as shown inFIG. 4. The conductive areas 11 j and 12 j are fastened so as to come incontact with each other via the screw 3 a shown in FIG. 1, so that theconductor 11 a and the conductor 12 a are always maintained in theconductive state.

The spacer 13 is used as an element for maintaining a predeterminedspacing between the conductor 11 a and the conductor 12 a. The spacer 13is interposed between the lower contact sheet 11 and the upper contactsheet 12 and it is made of a polyester film for electrically isolatingthese contact sheets 11 and 12 from each other. As shown in FIG. 5, thespacer 13 includes a through hole 13 c for connecting the conductorportion 11 j and conductor portion 12 j to each other; through holes 13d and 13 e for receiving the pins 6 a and 6 b respectively; and sixthrough holes 13 g for connecting the contact areas 11 g and thecorresponding contact areas 12 g to each other. The six through holesare disposed with the same circumferential distance in the same radialdistance from the center of the spacer 13.

The connector 14 is used as a connection element for electricallyconnecting the membrane switch 10 to electric wires, an electricalcircuit or an electrical appliance. As shown in FIGS. 2 and 3, theconnector 14 is connected to the conductor 11 a by inserting thereintoone end of the projection portion 11 b in which the conductor portions11 i and 11 k are formed.

In the following, the function of the membrane switch according to theembodiment of the invention will be described.

FIG. 6A is a sectional view of the membrane switch according to theinvention in the non-conductive state. FIGS. 6B and 6C are sectionalviews of the membrane switch according to the invention in theconductive state.

As shown in FIG. 6A, when the dial 4 in FIG. 1 is manipulated in thestate in which the upper contact sheet 12 is in contact with theprojection portion 9 d, a load or a press force resulting from thecontact with the dial 4 is transmitted from the projection portion 4 ato the projection portion 9 d via the force transmission element 9. As aresult, the projection portion 9 d moves the upper contact sheet 12downward by the press force applied thereto, as shown in FIG. 6B, sothat the upper contact sheet 12 is bent and the contact areas 11 g andthe corresponding contact areas 12 g are into contact with each other.As shown in FIGS. 2-4, the conductor 11 a having the contact area 11 gand the conductor 12 a having the contact area 12 g come into contactwith each other via the conductive area 11 j and conductive area 12 j.As a result, the conductors 11 a and 12 a are always maintained in theconductive state. Hence, the contact of the contact areas 11 g with thecorresponding contact areas 12 g causes the membrane switch 10 to be inthe conductive state (ON).

When a load resulting from the touching of the dial 4 is so small as toprovide a restricted contact between the contact areas 11 g and 12 g, asshown in FIG. 6C, the membrane switch 10 becomes in the conductive state(ON) as similarly to the case in FIG. 6B.

A decrease in the load or the press force applied to the projectionportion 9 d causes the projection portion 9 d to be moved upward by theresilient force of the upper contact sheet 12, and to be returned intothe initial position. As a result, the membrane switch 10 is transferredinto the non-conductive state (OFF).

The membrane switch according to the embodiment of the invention has thefollowing advantages:

(1) In accordance with the embodiment, the conductive areas 11 j and 12j enable the conductors 11 a and 12 a to be in contact with each otherand therefore to be always maintained in the conductive state. When apress force is applied to the contact areas 11 g and 12 g in theconductors 11 a and 12 a in such manner that they come into contact witheach other in a small area, the membrane switch 10 turns on into theconductive state. As a result, in the operation of the membrane switch10 according to the embodiment of the invention, no such large load isneeded, as in the conventional membrane switch 110, where a large loadhas to be applied between the contact area 112 a and the ramifiedcontact areas 111 c and 111 d, and therefore turns on in the conductivestate by applying a very small press force in touch sense, therebyenabling the reliability in the operation to be greatly enhanced. In themembrane switch 10, moreover, there is no need for firmly applying aresilient projection portion 109 d to the upper contact sheet 112 in theconventional membrane switch 110, thereby enabling the number of partsto be reduced as well as the production cost to be reduced.

(2) In accordance with the embodiment, the contact areas 12 g are alwaysconnected to the conductive area 11 j and, along with this arrangement,the membrane switch turns on, when at least one of the contact areas 11g and the contact area 12 g corresponding thereto come into contact witheach other. Due to this arrangement, the connector 14 of the membraneswitch 10 is compatible with the connector 114 of the conventionalmembrane switch 110 shown in FIG. 7. Accordingly, this arrangementensures an easy connection of the connector, compared with thearrangement in which two connectors are connected to the conductor 11 aand 12 a, respectively. In case of trying to form a connector 14 byextending the conductor portion 11 i from the contact areas 12 g,contacts of the connector have to be disposed in both the lower contactsheet 11 and the upper contact sheet 12, thereby lacking thecompatibility with the conventional connector regarding the contacts.

(3) In accordance with the embodiment, the contact areas 11 g and 12 gare disposed with the same circumferential spacing on a circle from thecenters of the lower contact sheet 11 and the upper contact sheet 12,respectively. As a result, the membrane switch 10 turns on steadily inthe conductive state, if a soft touch of at least one of the contactareas 11 g is carried out.

In the above-described embodiment, six contact areas 11 g and 12 g aredisposed on a circle. However, the number of the contact areas and thespacing therebetween can be arbitrarily selected. In the embodiment, anappropriate spacing can be provided between the contact areas 11 g andthe contact areas 12 g. Therefore, the press force necessary forcontacting the contact areas 11 g with the contact areas 12 g can beadjusted by appropriately selecting the thickness of the spacer 13 andthe inside diameter of the through holes 13 g. In the embodiment,moreover, the conductive area 11 j and the conductive area 12 j aredirectly in contact with each other. However, the electrical connectionbetween the conductive areas 11 j and 12 j can be attained via anappropriate conductive material. In the embodiment, however, the lowercontact sheet 11 and the upper contact sheet 12 are formed by the samematerial (for instance, polyester). Actually, the upper contact sheet 12can be formed by a flexible material. In this case, however, it is notnecessary that the lower contact sheet 11 and the spacer 13 are formedby a flexible material. In particular, the lower contact sheet 11 mustbe disposed on a flat surface of a stiff material in order to receivethe press force applied to the upper contact sheet. Otherwise, the lowercontact sheet 11 itself must be made of a stiff material. In theembodiment, furthermore, the conductor portions 11 i and 11 k on theside of the lower contact sheet 11 are connected to the connector 14.However, such conductor portions connected to the connector can beformed on the side of the upper contact sheet. In other words, thegeometry of the upper contact sheet 12 and the lower contact sheet 11can be arranged upside down, such that the contact sheets 11 and 12 aredisposed respectively on the upper and lower sides and the contact sheet12, in which case the lower contact sheet 11 can be made of a flexiblematerial.

While the preferred embodiment has been shown and described, variousmodifications and substitutions may be made without departing from thespirit and scope of the invention. Accordingly, it is to be understoodthat the present invention has been described by way of example, and notby limitation.

What is claimed is:
 1. A membrane switch comprising: (a) a first baseelement made of an electrical insulation elastic material, said firstbase element having a first conductor including at least one presscontact area and at least one permanent contact area on a surface ofsaid first base element; (b) a second base element made of an electricalinsulation material, said second base element having a second conductorand a third conductor on a surface facing said surface of said firstbase element, said second conductor including at least one press contactarea in accordance with the arrangement of said at least one presscontact area in said first conductor, and said third conductor includingat least one permanent contact area in accordance with the arrangementof said at least one permanent contact area in said first conductor,said second base element further having a connector section forconnecting said second and third conductors to an external circuit; and(c) a spacer made of an electrical insulation material, said spacerbeing interposed between said first base element and said secondelement, said spacer having through holes at positions corresponding tothose both in said at least one press contact area and said at least onepermanent contact area of said first and second base elements.
 2. Amembrane switch comprising: (a) a first base element made of anelectrical insulation elastic material, said first base element having afirst conductor including at least one press contact area, a secondconductor including at least one permanent contact area and a connectorsection for connecting said first and second conductors to an externalcircuit on a surface of said first base element; (b) a second baseelement made of an electrical insulation material, said second baseelement having a third conductor on the surface facing said surface ofsaid first base element, said third conductor including at least onepress contact area in accordance with the arrangement of said at leastone press contact area disposed in said first conductor and at least onepermanent contact area in accordance with the arrangement of said atleast one permanent contact area disposed in said first conductor; and(c) a spacer made of an electrical insulation material interposedbetween said first base element and said second base element, saidspacer having through holes in accordance with the arrangement of saidat least one press contact area and said at least one permanent contactarea.
 3. A dial operation member comprising: (a) a shaft; (b) a bearingthrough which said shaft passes; (c) a dial body fixed to said shaft androtatably supported around the center axis of said shaft; (d) a pressmember for switch disposed so at to face said dial body for switching,said press member having at least one press projection portion forswitching; and (e) a membrane switch according to claim 1 or 2, whereinat least one press portion for switching is disposed so as to face saidat least one press projection for switching in said press member forswitch.